Local Metric Learning for Tag Recommendation in Social Networks Using Indexing

1. A non-transitory storage medium storing instructions executable by a processing device to perform a tag recommendation method operating in conjunction with an electronic social network including user accounts and tagged items, the user accounts including user-user contacts information and each tagged item being indexed in the electronic social network by an item owner of the tagged item wherein the item owner is a user of the electronic social network, the tag recommendation method comprising: for an item to be tagged that is indexed in the electronic social network by an item owner of the item to be tagged, generating at least one tag recommendation for the item to be tagged by: (1) selecting a set of candidate neighboring items in the electronic social network wherein the selecting of the set of candidate neighboring items is limited to one of: selecting items from the set of items whose item owner is the item owner of the item to be tagged, selecting items from a set of items consisting of a combination of the set of items whose item owner is the item owner of the item to be tagged and the set of items whose item owners are users of the electronic social network who are contacts in the electronic social network of the item owner of the item to be tagged, and selecting items from a set of items consisting of a combination of the set of items whose item owner is the item owner of the item to be tagged and the set of items whose item owners are users of the electronic social network having between one and N degrees of separation inclusive from the item owner of the item to be tagged in the user-user contacts information of the electronic social network where N is an integer greater than or equal to two, (2) selecting a set of nearest neighboring items from the set of candidate neighboring items that are nearest to the item to be tagged as measured by an item comparison metric, and (3) selecting the at least one tag recommendation from tags of the items of the set of nearest neighboring items; and displaying, on a display, the at least one tag recommendation for the item to be tagged.

2. The non-transitory storage medium as set forth in claim 1 , wherein the selecting of the set of nearest neighboring items comprises: selecting K nearest neighboring items from the set of candidate neighboring items that are nearest to the item to be tagged as measured by the item comparison metric, where K is an integer greater than one.

3. The non-transitory storage medium as set forth in claim 2 , wherein the item comparison metric comprises a Mahalanobis distance metric operating on feature vector representations of items.

4. The non-transitory storage medium as set forth in claim 1 , wherein the item comparison metric comprises a Mahalanobis distance metric operating on feature vector representations of items.

5. The non-transitory storage medium as set forth in claim 4 , wherein the generating further comprises training the Mahalanobis distance metric on the set of candidate neighboring items wherein the training comprises optimizing a parameter matrix of the Mahalanobis distance.

6. The non-transitory storage medium as set forth in claim 4 , wherein the generating further comprises training the Mahalanobis distance metric on the set of candidate neighboring items to minimize an objective function comprising a sum of the outputs of the Mahalanobis distance metric operating on feature vector representations of candidate neighboring items with at least one overlapping tag.

7. The non-transitory storage medium as set forth in claim 4 , wherein the generating further comprises training the Mahalanobis distance metric on the set of candidate neighboring items to optimize a correlation between the trained Mahalanobis distance between two items and a metric indicative of tag set overlap between the two items.

8. The non-transitory storage medium as set forth in claim 1 , wherein the item to be tagged comprises an image to be tagged and the selecting of the set of candidate neighboring items comprises selecting a set of candidate neighboring images.

10. A tag recommendation method operating in conjunction with an electronic social network including user accounts and tagged items, the user accounts including user-user contacts information and each tagged item being indexed in the electronic social network by an item owner of the tagged item wherein the item owner is a user of the electronic social network, the tag recommendation method comprising: for an item to be tagged that is indexed in the electronic social network by an item owner of the item to be tagged, generating at least one tag recommendation for the item to be tagged by: training a Mahalanobis distance metric on a set of candidate neighboring items in the electronic social network to optimize a correlation between (i) the trained Mahalanobis distance between pairs of items i and j of the set of candidate neighboring items and (ii) an overlap metric measuring set overlap of the tag sets of the two items i and j wherein the overlap metric is proportional to |T i ∩T j | where T i denotes the tag set associated with the item i and T j denotes the tag set associated with the item j, selecting a set of nearest neighboring items from the set of candidate neighboring items that are nearest to the item to be tagged as measured by the trained Mahalanobis distance metric, and selecting the at least one tag recommendation from tags of the items of the set of nearest neighboring items; wherein the generating is performed by a digital processing device; and displaying, on a display, the at least one tag recommendation for the item to be tagged.

13. The tag recommendation method as set forth in claim 9 , wherein the generating further comprises: selecting the set of candidate neighboring items from one of: the set of items whose item owner is the item owner of the item to be tagged, a set of items consisting of a combination of the set of items whose item owner is the item owner of the item to be tagged and the set of items whose item owners are users of the electronic social network who are contacts in the electronic social network of the item owner of the item to be tagged, and a set of items consisting of a combination of the set of items whose item owner is the item owner of the item to be tagged and the set of items whose item owners are users of the electronic social network having between one and N degrees of separation inclusive from the item owner of the item to be tagged in the user-user contacts information of the electronic social network where N is an integer greater than or equal to two.

14. The tag recommendation method as set forth in claim 9 , wherein the selecting of the set of nearest neighboring items comprises: selecting K nearest neighboring items from the set of candidate neighboring items that are nearest to the item to be tagged as measured by the trained Mahalanobis distance metric, where K is an integer greater than one.